The prior art wire bonding machine is a conventional wire bonding machine, which does not have a wire bond force calibration meter.
The prior art wire bonding machine is used for the interconnecting of silicon dice within a hybrid. This machine bonds fine wires, made of gold or aluminum, from pads on the dice to pads on the hybrid substrate. The prior art wire bonding machine applies forces by means of a bonding stylus. The bonding itself occurs in two steps. Initially a light setup force is applied. The purpose of this is merely to hold the wire in place in preparation for the actual bonding. After a brief time, a dynamic bonding force is applied. The values of these forces are variable, and depend generally on the gauge of the wire being used. The heavier the gauge, the more force is required. However, the amounts are somewhat critical. Excessive force can fracture a die, causing reliability problems; too little can yield a weak bond. The range of force values normally encountered is from 20 grams to 1000 grams. The force values are set by dials on the prior art wire bonding machine.
One problem with the prior art wire bonding machine is that there is no way to measure the dynamic bonding force with relative accuracy. Another problem is that there is no way to automatically measure the static setup force. The static setup force can only be measured manually using a mechanical gauge, which is held by the operator underneath the bonding stylus during the initiation of the bond. The results obtained in this way are inconsistent, and are dependent upon operator dexterity to maintain the position of the gauge properly. The dynamic bonding force, which is transient in nature, lasting only 50 milliseconds in a typical case, cannot be measured with relative accuracy.